Auditory selective attention is impaired in Parkinson's disease - event-related evidence from EEG potentials

Selective attention refers to the ability to focus on one channel of information in the presence of distracting other channels. For the visual modality, results on impairments of selective attention have been conflicting in patients with idiopathic Parkinson's disease (PD). Independent of possible interferences from visual or movement disturbances selective attention can be measured as the so-called 'processing negativity' (PN) using auditory evoked potentials. Therefore, auditory selective attention with the PN was measured in 14 patients with PD and 16 control subjects. Subjects had to attend to tones presented to one ear (i.e. to press a button to occasionally presented longer tones) and ignore tones presented to the other ear. Tones were presented at a rate of 1/s ('slow') or 2/s ('fast'). PN was measured as the difference of the potentials evoked by attended minus ignored standard tones. PN was significantly smaller in the PD patients than in the controls with slow presentation. There was no difference between both groups with fast presentation. PN remained unchanged when patients had a 12-h withdrawal of their usual anti-Parkinsonian drug therapy. PD patients and controls did not differ in their P3 component evoked in the usual 'oddball' task nor in the mismatch negativity evoked by the occasionally longer tones in the PN task. The results provide evidence for an impairment of auditory selective attention that is specific for patients with PD (i.e. independent of the P3 component).